1. Field of the Invention
This invention relates to thermally stable, color-stabilized polycarbonates comprising halobisphenolethylene polycarbonates containing an effective amount of a stabilizing esterified hindered phenol.
2. Description of the Prior Art
The prior art has made limited observations regarding the properties of chlorobisphenolethylene polycarbonates such as the infra-red spectroscopic data by Z. Wielgosz, Z. Boranowska and K. Janicka, reported in Plaste und Kautschuk 19 (12) 902 (1972). Observations regarding attempts to stabilize chlorobisphenolethylene polycarbonates are reported by Z. Gobiczewski, Z. Wielgosz and K. Janicka in Plaste und Kautschuk 16 (2) 99 (1969) which describe the ineffectiveness of commercially available hindered phenols, e.g. Parmanox, i.e. 2,6-di-t-butyl-4-methylphenol, Topanol CA, i.e. 2,2,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, and Jonox 330, i.e., 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene as stabilizers for chlorobisphenolethylene polycarbonates at elevated temperatures, e.g. from 160.degree. to 260.degree. C. No other art is known of regarding attempts to stabilize chlorobisphenolethylene polycarbonates.
Unexpectedly, it has been found that certain esterified hindered phenols stabilize halobisphenolethylene polycarbonates against deleterious thermal effects -- as evidenced by reduced color degradation of esterified hindered phenol stabilized halobisphenolethylene polycarbonates after having been subjected to thermal stresses at elevated temperatures.